There may be no single cause of bipolar disorder (aka manic depression). Instead, research indicates the causes of bipolar disorder are probably a combination of biochemical, genetic and environmental factors that may trigger and perpetuate the chemical imbalances in the brain.
Net worth: $829 million. Telecommunications mogul Strive Masiyiwa is widely regarded as the richest man in Zimbabwe and is one of the richest men in Africa with a net worth of more than US$800 million.
Of the 1,645 people who made it to the 2014 FORBES list of the Worldâs Billionaires, 9 of them are black, up from 7 a year ago. Nigerian cement tycoon Aliko Dangote is still the richest black person in the world, and heâs the richest by a long shot â $9.7 billion richer than Saudi-Ethiopian billionaire Mohammed Al-Amoudi.